diff --git a/Makefile.in b/Makefile.in
index dbb8ae058..865b1aca5 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -233,7 +233,7 @@ lexor.cc: $(srcdir)/lexor.lex
 lexor_keyword.o: lexor_keyword.cc parse.h
 
 lexor_keyword.cc: $(srcdir)/lexor_keyword.gperf
-	gperf -o -i 7 -C -k 1-4,9,$$ -L ANSI-C -H keyword_hash -N check_identifier -t $(srcdir)/lexor_keyword.gperf > lexor_keyword.cc || (rm -f lexor_keyword.cc ; false)
+	gperf -o -i 7 -C -k 1-4,6,9,$$ -L ANSI-C -H keyword_hash -N check_identifier -t $(srcdir)/lexor_keyword.gperf > lexor_keyword.cc || (rm -f lexor_keyword.cc ; false)
 
 iverilog-vpi.man: $(srcdir)/iverilog-vpi.man.in version.exe
 	./version.exe `head -1 $(srcdir)/iverilog-vpi.man.in`'\n' > $@
diff --git a/autoconf.sh b/autoconf.sh
index bb7bb52a0..089c3ff93 100644
--- a/autoconf.sh
+++ b/autoconf.sh
@@ -10,4 +10,4 @@ echo "Autoconf in root..."
 autoconf -f
 
 echo "Precompiling lexor_keyword.gperf"
-gperf -o -i 7 -C -k 1-4,9,\$ -L ANSI-C -H keyword_hash -N check_identifier -t ./lexor_keyword.gperf > lexor_keyword.cc
+gperf -o -i 7 -C -k 1-4,6,9,\$ -L ANSI-C -H keyword_hash -N check_identifier -t ./lexor_keyword.gperf > lexor_keyword.cc